Osmosis is a phenomenon in which a solvent moves from a solution having a low solute concentration to another solution having a high solute concentration by passing through a semi-permeable separation membrane isolating the two solutions. In this case, pressure acting on the solution having a high solute concentration through the movement of the solvent is known as osmotic pressure. However, when external pressure having a level greater than that of osmotic pressure is applied, the solvent moves towards the solution having a low solute concentration, and such a phenomenon is known as reverse osmosis. Various types of salt or organic material may be separated by a semi-permeable membrane using a pressure gradient as driving force, according to the reverse osmosis principle. A reverse osmosis membrane using a reverse osmosis phenomenon has been used to separate molecular-level materials, remove salts from salt water or sea water and supply water available for domestic, commercial and industrial use.
The reverse osmosis membrane may representatively include a polyamide-based reverse osmosis membrane, by way of example. The polyamide-based reverse osmosis membrane may be manufactured by forming a polyamide active layer on a microporous support. More particularly, the polyamide-based reverse osmosis membrane may be manufactured by preparing a microporous support by forming a polysulfone layer on a non-woven fabric, dipping the microporous support into an aqueous m-phenylenediamine (mPD) solution to form an mPD layer, dipping the mPD layer into an organic solvent containing trimesoyl chloride (TMC) to allow the mPD layer to be brought into contact with the TMC so as to be interfacially polymerized to thereby form a polyamide layer.
However, the polyamide-based reverse osmosis membrane manufactured by the above conventional method may suffer from low initial permeation flux efficiency, resulting in deterioration of a water purifying function. Furthermore, in the case of water treatment using a reverse osmosis membrane, a solute or an ionic compound may be adsorbed to the surface of the reverse osmosis membrane to pollute the reverse osmosis membrane, and thus, water permeability characteristics such as permeation flux and salt rejection have been degraded over time.
Therefore, research into development of a reverse osmosis membrane having superior durability as well as improvements in water permeability characteristics such as permeation flux and salt rejection is urgently in demand.